Human skin consists of two compartments, namely a surface compartment, the epidermis, and a deep compartment, the dermis.
Natural human epidermis is composed mainly of three types of cells: the keratinocytes, which form the vast majority, the melanocytes and the Langerhans cells. Each of these cell types contributes via its intrinsic functions to the essential role played by the skin in the body.
During the process known as keratinization, the keratinocytes located in the basal layer of the epidermis multiply and grow, thus pushing the older epidermal cells upwards and towards the surface of the epidermis. During this displacement, these cells become flattened and differentiate to form keratin. The dead surface cells resulting from this keratinization process (corneocytes) constitute the horny layer of the epidermis, where they are separated by lipid layers and linked together via protein linkages (corneosomes). These dead cells are gradually removed from the surface of the skin and replaced with new keratinized cells.
In young, healthy skin, the desquamation of the skin that takes place in this way is characterized by the removal of individual cells or of small lumps of cells. In contrast, with age or in the case of certain pathologies, desquamation may be impaired, in the sense that an excess of keratin material is formed at the surface of the skin, resulting either in a removal of the stratum corneum in the form of squamae (ageing of the skin or dry skin), or in an obstruction of the sebaceous follicles (acne).
The use of desquamating agents, such as α-hydroxy acids and β-hydroxy acids (in particular salicylic acid), is thus generally indicated in the cosmetic or dermatological treatment of the abovementioned skin disorders.
It nevertheless remains that the desire to maintain a youthful appearance and/or healthy skin continues to lead to the incessant search for novel compounds and/or novel compositions for maintaining or improving the appearance of the skin.